KR20060097650A - Method and plant for the continuous production of sheets of foamed material - Google Patents

Abstract

The present invention relates to a method and a plant for producing sheets of material to be foamed in a continuous foam process, in which the actual foam profile of the foamed material is detected parallel to the direction of travel of the conveyor belt, and from the target or reference foam profile Calibration parameters for the foaming process are determined as a function of the variation of the foaming profile, and the process parameter (s) are / adjusted to correspond to the actual foaming profile relative to the reference foaming profile.

Continuous foam process, material being foamed, plant, foam profile, process parameters.

Description

METHOD AND PLANT FOR THE CONTINUOUS PRODUCTION OF SHEETS OF FOAMED MATERIAL}

1 is a schematic illustration of a preferred embodiment according to the present invention in which a process for continuously producing a sheet of foamed material is carried out using a twin belt conveyor plant.

Figure 2 shows a foam expansion profile with little overlap.

Figure 3 shows a foam expansion profile with heavy overlap.

4 shows a foam profile without any overlapping;

<Short description of drawing symbols>

1: conveyor belt

2: conveyor running direction

3: mixing head

4: coating plate

5: expanded foam

6: lower cover layer

7: top cover layer

8: roller

9: measuring device

10: foamed profile

11: busbar system

12: adjuster

13: Foamed profile with little overlap

14: Foamed profile with heavy overlapping

15: Foamed profile without overlapping

The present invention relates to a method and a plant for producing sheets of material, in particular polyurethane foam sheets, which are foamed in a continuous foam process.

In the manufacture of flexible block molded foamed materials, various computer controlled methods for predicting foaming properties and ensuring quality during the production of polyurethane foams are described, for example, in flexible polyurethane foams by the block foam technology. Software to Manage a Continuous Production of Flexible Polyurethane Foams by Slabstock Technology ", March 1997, Volume 33, page 102 (Journal of Cellular Plastics, Volume 33, March 1997, page 102), And "Mathematical Property Prediction Models for Flexible Polyurethane Foams", 1998 AD, Urethane SCS. Technology page 1-44 (Adv. Urethane Sci. Techn. 14 (1998), pages 1 to 44).

For the purpose of optimizing productivity and quality, so-called RIM methods are known, called expert systems. [Experten mit System, Prozesssteuerung des PUR-RRIM-Verfahrens zur Herstellung von Karosserieaussenteilen], Kunststöpe, Vol. 88, 10/98 (Kunststoffe, 88th annual set, 10/98) and "cost-saving fabrication of PUR parts, the current state of polyurethane-RRIM technology", Kunststoffe, Vol. 91, 4/2001 (Kunststoffe, 91st annual set, 4/2001), an expert system for analyzing process parameters during the RIM process is described. These expert systems assist in process monitoring, quality assurance and preventive maintenance.

DE 28 19 709 B1 describes a method for the continuous production of foam sheets provided with a cover layer, wherein the thickness of the foam is detected by ultrasound at right angles to the direction of travel. The manufacturing plant is thus controlled by the speed of movement of the conveyor belt and / or the amount of foam applied. The control algorithm described in this method contributes to reducing quality damage, operational interruptions and labor costs.

DE 102 37 005 A1 describes a method for monitoring a continuous block molding foam process which continuously detects the foam profile in the form of local foam heights along the conveyor apparatus. Laser distance sensors are preferably used for this purpose. Modification parameters used to control the block forming process are identified as a function of the possible deviation between the actual foam height and the preset fixed foam height.

The production of metallic composite elements by continuous or discontinuous methods is known. Devices for continuous production are described, for example, in DE 1 609 668 A, DE 1 247 612 A or DE 92 16 306 U1.

In addition, various types of plants are known for producing polyurethane rigid foam sheets or polyurethane rigid foam composite sheets continuously or discontinuously. For example, polyurethane rigid foam sheets are produced using twin belt conveyor plants. Plants of this type are for example Hennecke GmbH, Birlinghoverner Strasse 30, 53754 Sankt Augustin, Germany under the name CONTIMAT®. Commercially available from.

In order to produce high quality and reproducible products during the continuous production of polyurethane foam sheets, a stable operating state should be pursued as possible. This state is obtained if the overall foam profile retains the desired shape and remains static within certain limits associated with the environment, or more precisely with respect to the molding press. For this purpose, the reaction process of the polyurethane system, the amount of foam applied, the speed of the belt, and the temperature control of the overall plant and raw material components must be in harmony with each other.

DE 196 16 643 C1 describes a method for producing a sheet of foaming material, wherein the lateral separation foaming from the anchoring point is measured upstream of the inlet of the press. The actual value of the separation is compared with a target value which depends on the material being foamed, and the operating speed of the plant is controlled according to the deviation between the actual value and the target value. The formulation of the polyurethane system and consequently the kinetics, the amount of application of the reaction mixture and the temperature of the plant are not taken into account.

Using adjusted formulas, known height and width values of the sheet of material being foamed, and fixed production rates, in theory the speed of the plant is such that the foam fills the spaces between the cover layers in the forming chamber press and compression of the foam occurs. Should be able to be chosen in a way that does not. In practice, such adjustments are not possible and not necessarily required. The space between the cover layers must be completely filled with foam. For this purpose, certain compression of the reaction mixture is necessary, without excessive deflection of the mixture in the opposite direction to the direction of travel of the belt. This deflection is called overlapping. Some overlapping may be desirable in some cases, depending on the product, as the fragile wavy surface of the reaction mixture foaming in this way is smooth and no bubbles or air holes are formed under the top cover layer. Excessive overlapping results in greater friction between the foam and the top cover layer or the top wall of the press. Foam cells elongate in the advancing direction of the belt, thereby impairing the compressive and tensile strengths in the thickness direction of the sheet. In this way, vertical cracks may also be formed in the foam sheet. Overlapping of the foams, on the other hand, leads to flat cells which are particularly redirected in the region of the top cover layer. Generally this results in lower thermal conductivity values and may be desirable for certain applications.

Due to the exothermic nature of the polyurethane foaming reaction, the temperature controlled molding chamber press of the manufacturing plant is further heated during the manufacturing process. Since this has an effect on the reaction rate and consequently on the degree of overlap with the foam profile, control countermeasures must be taken during operation. This can only be achieved by harmonizing the modification of the sheet of foamed material to be produced, the production rate, the application amount, the process temperature and the geometry.

Foam expansion profiles and, in particular, overlapping, have to be adjusted for the specific product being manufactured. In order to achieve a consistent quality of the sheet of material being foamed, care must be taken to ensure that the foam expansion profile and consequently the overlapping remain the same throughout the entire manufacturing process and at each load. The exact positioning of the profile is not critical within certain limits.

A "foam expansion profile" is understood as an overall foam expansion profile that can be visualized by an observer watching the foam form from the onset of expansion until the foam reaches the top cover layer and expand parallel to the direction of travel of the conveyor belt.

The present invention provides improved monitoring and improved control over the production of a sheet of material foamed in a continuous foam process by detection of a foam profile parallel to the traveling direction of the conveyor belt in the plant, in particular overlapping. The actual foaming profile and the actual overlapping are compared with the target profile (also referred to as the "reference profile") specifically set by the formula. Calibration parameters for readjustment of the process from possible deviations of the actual profile from the target profile are reviewed. In contrast to DE 196 16 643 C1, control is provided by the detection of relative values derived from the actual profile and the target profile, not by the detection of exact separation from a fixed point.

A particular advantage of the present invention is that qualitative and quantitative monitoring of the foaming operation can be made at an early point in the manufacturing cycle. In addition, the parameters of the plant and / or the composition of the foam forming material can be adjusted during the manufacture of the foamed material, thus achieving a constant product quality possible. As a result, variations in product properties such as, for example, compressive strength, are reduced due to various foam expansion behaviors or changes in overlapping.

Another advantage of the present invention is that the time for start-up of the plant is shortened by the detection of foam expansion profiles and overlapping already with the start of manufacture. In this way it is possible to reduce the consumption during start-up of the manufacturing plant.

According to the invention, a device for detecting foam expansion profile or overlapping is mounted upstream of the inlet of the press and parallel to the direction of travel of the conveyor belt. The detection device preferably comprises several laser distance sensors, which are arranged on top of each other and / or at an offset in such a way that the actual profile of the foam can be measured. Alternatively or additionally, ultrasonic sensors, photoelectric sensors, CCD cameras or other sensors capable of measuring the foam profile can be used. In another preferred embodiment, a laser scanner is used which detects the foam expansion profile in two dimensions at right angles to the conveyor direction. For this purpose, the laser line is preferably projected onto the foam and the profile height is determined by triangulation. The contour of the foam can be made over the entire cross section of the sheet using several scanners at right angles to the conveyor direction or by turning the laser line.

In a preferred embodiment of the invention, the foamed material is produced in a twin belt conveyor plant, for example in a plant of the type commercially available from Hennecke under the trade name Contimat. The plant usually has a conveyor device, on which foaming material which expands moves in the direction of conveyor travel. In general, the work in the plant proceeds with a flexible and / or rigid cover layer. The cover layer is guided into the forming chamber press by a conveyor belt.

In another preferred embodiment of the present invention, scanning of the foam profile is performed at each position, a suitable curve is created by the measured actual profile value of the foam, and the suitable curve is compared with the target curve. For example, the difference between the slopes of the curve or the difference in the integral values of the curves in the expansion region is used as the basis for determining the calibration parameter.

According to another preferred embodiment of the invention, the conveyor running speed of the expanding foam is used as a calibration parameter. For example, if the integral value of the foam profile in the foam differs from the predetermined target profile in such a way as to cause excessive overlapping, the conveyor running speed is increased until the actual profile is sufficiently consistent with the target profile.

According to another preferred embodiment of the present invention, the amount of material fed to the block forming foam process per unit time is used as a calibration parameter. For example, if the integral value of the foam profile in the foam differs from the predetermined target profile in such a way as to cause excessive overlapping, the amount of material supplied per unit time is reduced until the actual profile and the target profile are sufficiently matched. .

According to another embodiment of the invention, the chemical composition of the material fed to the block forming foam process is used as a calibration parameter. For example, if the actual profile and the target profile are too different from each other, the chemical composition is changed until the actual profile is sufficiently consistent with the target profile. Specifically, the amount of catalyst and / or the amount of physical blowing agent (eg pentane) added and / or water as chemically active blowing agent can be varied.

According to another embodiment of the invention, the temperature of the reaction component is used as a calibration parameter. For example, if the actual profile and the target profile are too different from each other, the temperature of the reaction component is changed until the actual profile and the target profile coincide again.

According to another embodiment of the invention, the temperature of the cover layer of the forming chamber press is used as a calibration parameter. For example, if the actual profile and the target profile are too different from each other, the temperature of the cover layer of the forming chamber press is changed until the actual profile sufficiently matches the target profile.

According to another embodiment of the present invention, for example, a change in the conveyor running speed, a change in the temperature of the forming chamber press or cover layer, a change in the amount of material supplied per unit time, and / or a chemical composition of the supplied material Some different calibration parameters, such as change, are determined based on the deviation of the actual profile from the foam's target profile.

According to another embodiment of the present invention, at least one manufacturing characteristic of the foam material sheet produced is predicted based on the actual profile of the foam. For example, the tensile strength and / or compressive strength of the foam sheet can be predicted. Strict regression models can be used for this prediction. Alternatively or in addition, a neural network or a hybrid neural network can be used for prediction. The modification of the reaction mixture, the conveyor running speed, the temperature of the forming chamber press and cover layer and the amount of material supplied per unit time are used as further input variables for the example.

According to another embodiment of the invention, the predicted product properties are used to classify the quality of the foamed material sheet produced. For example, predicted properties are used in the database.

According to another embodiment of the invention, the region of low quality foaming material produced is identified based on predictions for at least one product characteristic. The area is cut from the sheet of material to be foamed. Compared to the state of the art, the present invention has the advantage that less material is disposed of.

In most cases, sheets of a predetermined length (eg 6 m) are cut from the foam sheets in a continuous production process of foam sheets, and each sheet is then subjected to a quality check. On the other hand, the method according to the present invention allows for classified and suitably classified with differentiating quality grades for low quality predicted foam sheets.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

1 shows a preferred embodiment of the present invention. Specifically shown is a twin belt conveyor plant for continuously producing foam sheets from polyurethane foam. The plant has a conveyor belt 1 which moves in the conveyor running direction 2. At the beginning of the conveyor belt 1 a mixing head 3 is located above the conveyor belt 1. The mixing head 3 is used to apply a reactive chemical system onto the applicator plate 4 of the conveyor belt 1. Reactive chemical systems are, for example, foam mixtures for producing polyurethane foams.

The reactive chemical mixture expands on the conveyor belt 1 to form an expansion zone with the expanding foam 5. The foam is applied on the lower cover layer 6. In addition, the cover layer 7 is applied on top. Cover layers 6 and 7 may be flexible and / or rigid materials. Examples of materials useful as cover layers for insulation plates include kraft paper, tar paper, asphalt impregnated cardboard, corrugated paper, PE-coated glass mats and aluminum foil. Structural elements having rigid cover layers on both sides are provided with lacquered or coated steel sheets, stainless steel sheets, wood sheets, aluminum sheets, or GRP cover layers. When rigid boards (eg chipboard, gypsum board, fiber reinforced cement board, fiberglass board, rock wool board or pearlite board) are used as the bottom cover layer and a rollable outer layer is used as the top cover layer , A compounding sheet (composite) is obtained. The cover layer is fed through the roller 8. The foam mixture reaches the top cover layer 7 in the belt channel. By defined separation of the upper belt from the lower belt, this area of the plant functions as a press and ensures accurate sheet thickness.

The measuring device 9 is mounted directly downstream of the mixing head. The measuring device 9 measures the foam profile 10 in the expanded region of the foam. The measuring device 9 is connected via a bus bar system 11. The busbar system 11 is connected to the regulator 12. Through busbar system 11, regulator 12 receives a measurement signal from measuring device 9. Based on this measurement signal, the regulator 12 examines calibration parameters for readjusting the foam process. For example, the speed of the conveyor belt 1 and / or the amount of reactive chemical system supplied per unit time through the mixing head 3 and / or the chemical composition of the system and / or the temperature of the applicator plate 4 and And / or the temperature of the raw material components and / or the temperatures of the cover layers 6 and 7 are used as calibration parameters.

2 shows a foaming profile with little overlapping 13. Just below the upper cover layer 7 the foam flows in the opposite direction of the conveyor travel 2. 3 shows a foaming profile in which the overlapping 14 is severe, where the foam under the upper cover layer 7 flows to a considerable extent in the opposite direction of the conveyor travel direction 2. 4 shows a foaming profile without overlapping 15, in which no foam flows under the upper cover layer 7 in the conveyor running direction 2.

In order to perform closed loop control, the difference between the actual profile and the target profile is evaluated. Such an evaluation can be made in such a way that the adaptation curve is created by the actual profile value measured by metrology, for example. In this regard, it may be directed to a regression line or polynomial, for example spline polynomial or ripple.

To determine the calibration parameters, different slopes of the actual profile curve and the target profile curve can be created, ie the difference between the curve slopes is determined. This difference constitutes a measure of the deviation of the actual profile from the target profile.

Alternatively or in addition, the integral value of the actual profile curve and the target profile curve can be formed. In addition, the difference between the two integral values provides a measure of the deviation of the actual profile from the target profile.

Alternatively or in addition, the inflection points of the actual curve and the target curve can be used to determine calibration parameters. Typically, for foam profiles with overlapping, curves with inflection points are obtained that can be used to determine calibration parameters.

Based on the deviation between the actual profile and the target profile, calibration parameters are investigated for control purposes of the foam process. If the actual profile differs from the target profile, for example the speed 1 of the conveyor belt can be adjusted. Alternatively or additionally, the amount of reactive chemical system applied by the mixing head 3 per unit time, the composition of the reactive chemical system and / or the process temperature (eg, the temperature of the reaction component or the cover layer). Temperature) can be adjusted.

Closed loop control of the foam process takes place via the regulator 12. The regulator 12 includes a module for determining the actual profile. The regulator 12 further includes a module for comparing the measured actual profile with the stored target profile. The measurement index representing the measurement of the deviation of the actual profile from the target profile is computed. This measurement index is used to measure calibration parameters to readjust the process.

The plant further has a computer system (not shown) with a module for predicting at least one product specification of the foam material sheet to be produced, a table for classifying the predicted quality of the foamed material to be manufactured, and a database. . In the database, the predicted product quality in the longitudinal direction of the foam sheet can be stored, ie the product quality for a particular point in the foam sheet produced continuously is stored in the database. The computer system receives the actual profile by the input variable. Alternatively, the measured actual profile value is entered. In addition, an irradiated measured index indicating a measured value of the deviation between the actual profile curve and the target profile curve can be input into the computer system.

Based on these inputs, one or more product properties of the foaming material that is currently being manufactured are predicted. The predicted product properties can be, for example, compressive strength or tensile strength.

By the predicted product characteristic, a quality classification is made according to the quality of the product by applying a table in which allowable allowable values for the product characteristic are stored. Thus, the predicted product properties and the quality assigned to the foaming material currently being manufactured are stored in a database.

Usually, the foam material produced by the continuous foam process is cut into sheets, for example 6 m long. The plant has a cutting device (not shown) for this purpose. Such a cutting device is preferably activated by a computer system. If the computer system predicts that it will have a lower quality for a portion of the foam sheet that is continuously manufactured, this portion is cut from the foam sheet upon activation of the cutting device. In this way, waste in the foam process can be reduced.

One embodiment of the prediction module is a neural network. The input variables of the neural network are the actual foam profile, the composition of the reactive chemical system applied on the conveyor belt 1 by the mixing head 3, and the parameters of the plant, for example pressure and temperature, and also preferably Is an environmental parameter such as, for example, atmospheric pressure. From these input parameters the neural network predicts one or more product characteristics. The training necessary for the training of the neural network can be obtained by a separate series of experiments or by the approval of the data keeping the current manufacturing run.

While the present invention has been described in detail above for purposes of illustration, such details are for the purpose of this purpose only and modifications thereof do not depart from the spirit and scope of the invention, except as may be defined by the claims. It should be understood that it can be made by those skilled in the art.

According to the invention, improved monitoring and improved control are provided for the production of a sheet of material which is foamed in a continuous foam process by the detection of a foam profile parallel to the traveling direction of the conveyor belt in the plant, in particular overlapping.

Claims (29)

A process for producing sheets of material foamed in a continuous foam process, a) detecting the actual foam profile for the foam forming mixture provided parallel to the direction of travel of the conveyor belt, b) determining calibration parameters for the foam process as a function of the deviation of the actual foam profile of the foam forming mixture from the reference foam profile, and c) adjusting the foam process by changing calibration parameters such that the actual foam profile of the foam forming mixture corresponds to the reference foam profile. The method of claim 1 wherein the material to be foamed is a polyurethane foam. The process of claim 1 wherein the continuous foam process is performed using a twin belt conveyor plant. The method of claim 1, wherein the actual foam profile is detected with a measuring sensor. The method of claim 1, wherein the conveyor running speed is a calibration variable. The method of claim 1 wherein the amount of material fed to the foam process per unit time is a calibration parameter. The method of claim 1 wherein the chemical composition of the material fed to the foam process is a calibration parameter. The method of claim 1 wherein the temperature of the material fed to the foam process is a calibration parameter. The method of claim 1 wherein the temperature of the applicator plate is a calibration parameter. The method of claim 1 wherein the temperature of the cover layer fed to the foam process is a calibration parameter. The method of claim 1 wherein the temperature of the forming chamber press is a calibration parameter. The method of claim 1, wherein at least one product property of the sheet of foamed material located in the area along the conveyor running direction of the foamed material is predicted as a function of the actual foam profile. The method of claim 12, wherein the prediction of product characteristics is made by a regression model. The method of claim 12, wherein the prediction of product characteristics is made by a neural network or by a hybrid neural network. The method of claim 14, wherein the actual firing profile is entered into the neural network as an input parameter. 13. The method of claim 12 wherein the product properties are used to classify the quality of the material being foamed. The method of claim 16 wherein the area of low quality foamed material is cut. A plant for producing materials that are foamed in a continuous foam process, a) means for detecting the actual foam profile of the sheet of material being foamed, b) a plant comprising means for determining calibration parameters for the foam process as a function of the deviation of the actual foam profile from the predetermined reference foam profile. 19. The plant of claim 18 comprising a twin belt conveyor device. 19. The plant of claim 18, wherein the means for detecting the actual foam profile comprises at least one laser distance sensor or laser scanner or ultrasonic sensor or CCD camera. 19. The plant of claim 18, wherein the means for determining calibration parameters is an apparatus for determining the conveyor running speed of the foam forming mixture. 19. The plant of claim 18, wherein the means for determining calibration parameters is a device capable of determining the amount of foam forming material to be fed to the foam process per unit time. 19. The plant of claim 18, wherein the means for determining calibration parameters is a device capable of determining the chemical composition of the material to be fed to the foam process. 19. The plant of claim 18, wherein the means for determining calibration parameters is a device capable of determining the temperature of the material fed to the foam process. 19. The plant of claim 18, wherein the means for determining calibration parameters is a device capable of determining the temperature of the applicator plate. 19. The plant of claim 18, wherein the means for determining calibration parameters is an apparatus capable of determining the temperature of the cover layer fed to the foam process. 19. The plant of claim 18, wherein the means for determining calibration parameters is a device capable of determining the temperature of the forming chamber press. 19. The plant of claim 18, further comprising means for predicting at least one product characteristic of the material being foamed as a function of the actual foam profile, said means being located along the conveyor running direction of the foam forming mixture. 29. The plant of claim 28, further comprising control means of a cutting device for cutting the material to be foamed into a sheet having predicted product properties.

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